Optical networking and telecommunications systems have evolved substantially over the last five to ten years, not only in capability and efficiency, but also in complexity. Yet, while systems have evolved, the demands of the marketplace have continued to fuel the need for improvements.
One area of improvement is in the manufacture of network components. Many optical and opto-electronic devices are used in modern telecommunication networks. Optical filters, amplifiers, oscillators, arrayed waveguide gratings (AWGs), switches, and Mach-Zehnder interferometers are common examples. The manufacture of these and other devices has been an over costly endeavor in which devices are individually fabricated, often to tailor the devices to very specific applications of use. Such individual device fabrication approaches prevent device manufacturers from relying upon cost-saving batch fabrication techniques and efficient assembly techniques. These limitations also hinder the fabrication of optical modules assembled using component co-packaging, i.e., structures in which multiple components are formed within a single, integrated module. This latter limitation is particularly problematic, because optical component integration offers numerous theoretical advantages, of which device efficiency and speed are two of the most important.
Currently, a common method of creating multi-functioning optical modules, is to make discrete functioning optical components and then couple the components together through waveguide or lens couplings. Optical fiber pigtails are an exemplary means of coupling a signal from the output port of one device to the input port of another device.
Some manufacturers have produced multiple device modules, where individual devices are connected via very short optical fiber segments or miniature lenses. Such modules reduce the separation distance between devices, but, nevertheless, still limit the spacing between devices. That is, these solutions do not offer a small enough integration scale for the module. The couplers may be removed to allow free-space coupling between devices, but such coupling is incompatible with the preferred module assembly techniques.
For device assembly, manufacturers rely upon pick-and-place assembly techniques to mount the various optical devices onto a substrate. While exact component placement on the substrate is ideal, cost-effective pick-and-place assembly often results in small misalignments in device placement, i.e., the placement of devices on the substrate in positions other than the exact placement positions set-forth in the design schematic. Some of these misalignments are large enough to affect the coupling between individual devices within a module. In fact, one of the advantages of fiber and lens couplers is that they may correct for these misalignments between devices due to pick-and-place assembly, while free-space coupling does not correct for such misalignment. The problem is that using known couplers reduces module integration by increasing the spacing between the devices in the module. Furthermore, these couplers themselves must be manufactured separately from the optical devices to be placed in the module.
Alignment of the various devices in an optical module can be optimized but only by using expensive alignment techniques. Alignment between devices may be done manually or with the aid of very precise machine vision systems. These solutions slow device manufacture times substantially and are costly. Alignment may be achieved by using automated pick-and-place assembly techniques that are automated for a very high degree of accuracy, but again this slows the assembly process and adds substantial cost.